. This piece owes
whatever popularity it may have preserved to the sturdy swing of the
main theme and to the fact that it makes no demand on the attention of
the most untrained listener. In fairness we should state that on the
harpsichord--with its contrasting stops and key-boards--for which the
piece was composed, there is possible more variety of effect than on
the modern pianoforte.

[Footnote 80: We would cite the piece entitled _Les Buffons_ by Bull,
and Byrd's variations to the popular tune the _Carman's Whistle_,
which latter have considerable archaic charm and distinction; for Byrd
was a real genius. These are readily accessible in popular editions.]

[Footnote 81: Consult the comprehensive article on Variations in
Grove's Dictionary, Vol. V.]

Three collateral early forms deserve a passing mention because,
notwithstanding a certain rigidity of structure, they have been used
by the great masters for the expression of sublime thoughts. These are
the Ground Bass (or, as it is sometimes called, the Basso Ostinato),
the Chaconne and the Passacaglia[82] which, in modern literature, is
well represented by the magnificent "tour de force" that serves as the
Finale to Brahms's _Fourth Symphony_. By a Ground Bass is meant a
theme, continually repeated, in the lowest voice, each time with
varied upper parts. An excellent example (see Supplement No. 39) is
the Aria "When I am laid in earth" from Purcell's Opera _Dido and
Aeneas_. It is evident that the persistent iteration of a striking
phrase in the bass gives an effect of dramatic intensity, as may be
seen in the sublime "Crucifixion" of Bach's _Mass in B minor_.[83]
The Chaconne and Passacaglia are old dance forms (examples of the
former being found in Gluck's Ballet Music) and are closely related to
the Ground Bass; since, in the majority of cases, we find the same
procedure in the announcement of the theme and in its subsequent
treatment. Two examples of the Chaconne from standard literature are
the famous one of Bach in D minor for solo violin and Beethoven's
thirty-two Variations in C minor for Pianoforte. The Passacaglia is of
importance as shown by the striking example for organ in C minor by
Bach on the following theme:

[Music]

Whoever has heard this majestic theme, which seems to bear the sorrows
of the world on its shoulders, announced on the deep-sounding pedals
will gain a lasting impression of the grandeur of Bach's style.

[Footnote 82: For the der